Electromagnetic trip



Jan. 22, 1957 A. R. LARDIN ELECTROMAGNETIC TRIP 2 Sheets-Sheet 1 Filed Aug. 4, 1954 III IN VENTOR I j HIS ATTORNEY A. R. LARDIN ELECTROMAGNETIC TRIP 2 Sheets-Sheet 2 INVENTOR ArfhurR. Lard/"n BY QL 7" HIS ATTORNEY Jan. 22 1957 Filed Aug. 4. 1,954

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Development Laboratories, Inc., Dallas, Tex., a cor-.

poratron Application August 4, 1954, Serial No. 447,840 6 Claims. (Cl. 74--2) My invention relates to an electromagnet tripping or releasing device, especially to an electromagnetically operated release mechanism employed in an aircraft bomb release system to operate bomb suspension shackles.

An object of my invention is the provision of a lighter and smaller bomb release mechanism than heretofore known comprising a minimum ofparts which can be easily assembled and disassembled, and which is capable of acting positively with a high degree of speed and force.

Another object is to provide a release mechanism of general purpose operated by electromagnetic means in which failure under operating conditions is eliminated and in which the possibility of premature release under shock loads is virtually impossible.

Other objects and advantages of my invention, in part, will be obvious and in part pointed out hereinafter during the course of the following description.

My invention accordingly resides in the combination of elements, features of construction, and arrangements of parts, the scope of the application of all of which will be more fully set forth in the claims at the end of this specification.

For a more ready comprehension of my invention, reference is had to the accompanying drawings, wherein:

Fig. 1 is a perspective view of the electromagnetic trip of my invention shown in place upon a conventional bomb release shackle.

Fig. 2 is a longitudinal sectional view of my invention as shown in cocked position.

Fig. 3 is a sectional view taken substantially along line 3-3 of Fig. 2.

Fig. 4 is a sectional view taken substantially along line 4-4 of Fig. 2;

Fig. 5 is a detailed perspective of the core of Fig. 2.

Fig. 6 is a side elevation partly in section showing the mechanism of Fig. 2 in released position.

Like reference characters refer to like parts throughout the several views of the drawing.

As conducive to a clearer understanding of my invention, it may be noted at this point that in the past spring loaded rods or plungers have been employed to actuate bomb shackles and thereby release bombs selectively from their suspension racks. Generally, these plungers or rods have been retained in the cocked position by holding means which are released by electrical means to enable the plunger to move forward under the action of the spring. The force of the plunger end striking the bomb shackle moves it to a position which permits release of the bomb. Various release mechanisms have been proposed incorporating a variety of holding means. it has been found, however, that these prior art mechanisms are susceptible to actuation by shock, particularly that created when the aircraft is under rapid accelerating or decelerating conditions such as a crash landing and violent maneuvering in combat such as rolls and spins. These shock loads cause premature actuation of the release mechanism and consequent premature release .of the bomb. On the other hand, with the attempt to cor- States atet 2,778,226 Patented Jan. 22, 1957 2 rect for the inherenttendency toward premature release there was encountered the problem of possible failure of the mechanism to act when energized.

It is therefore an outstanding object of my invention to provide a bomb release mechanism which willnotprematurely release under shock loading and which is'Of smaller size and weignt than known previously while exerting a much greater force to insure that the proper release action is secured when desired. The release mechanism while performing with optimum results under all conditions is constructed of a minimum of parts for easy assembly and disassembly and can be reset. after release with a single manual movement.

Referring now more particularly to the practice of my Q invention, I provide a hollow tubular guide member that t has a shoulder at its forward end containing grooves in its forward face. This is provided with two sets of radially spaced lock holes, one set being at a point adjacent the shoulder and the other at the guide aft end. I also provide a plunger shaft countersunk at either end'that is arranged to reciprocate longitudinally within the guide tube. The forward end of the plunger shaft has a plunger head that is urged in a forward direction by one or more coil springs under compression.

Forward movement of the plunger is prevented by means of locking balls fitting into each of the holes at either end of the guide tube. When the plunger shaft is manually pushed inwardly against the forces of the springs to the cocked position these balls seat within depressions provided with the periphery of the plunger shaft locking the shaft in position as noted.

Surrounding the central portion of the guide tube 1 provide a tubular core, both ends of which are beveled inwardly. At either end of the core I position a longitudinally movable cylindrical magnetic armature ring which has a beveled end to provide a meeting face with the core. Springs are located between the core and armatures to normally urge the armature outwardlyfrom the core.

In order to attract the armatures towards the core against the spring biasing, and expose recesses in the armatures to the locking balls, I provide a solenoid coil surrounding the magnetic core which when energized causes the armatures to sharply come up against the beveled faces of the core and force the balls to move out of locking engagements with the plunger shaft. I 2

also provide additional shallow grooves on the plunger shaft into which the locking balls can seat when the plunger is in the released'position. At the aft end of the plunger shaft a forward stop conveniently is provided.

For alignment purposes I provide a metallic forward ring adjacent the guide tube shoulder and an aft ring at the rear end of the solenoid coil. The assembly is encompassed within a hollow shell which is suitably secured thereto. surrounds the plunger and its actuating springs, being attached at one end to the hollow shell and at the other end to the plunger head. I also provide an aft stop member behind the aft end ring. Suitable contact pins also are provided at the aft end to which are connected the leads from the solenoid coil.

As specifically illustrative of the structure of my invention, attention is directed to Figs. 1-6 of the drawing.

Shown in Fig. l is a conventional bomb release shackle cated at M. The electrical connections for the mecha- A flexible boot of the bellows type I V s nism are not shown as they form no part of this invention.

Referring now to Fig. 2, the release mechanism 12 is shown in the cocked position before releasing. This consists of a tubular metallic shell 13 within which a solenoid coil 14 is positioned. 'Coil v14 is cylindrical in shape, defining an inner opening, with windings which terminate in leads 15 connected to a pair of contact fingers 16; Contacts 16 may be connected to any source of D. C. or A. C. electrical power to permit energization of the coil 14 selectively.

A metallic core 17 of permeable metal is placed within the center portion of the coil 14 and is fixedly positioned by means of pins 18 to a guide tube 19. The corecontains three radial holes 20 equally spaced around its center periphery as shown in Fig. 3 into which pins 18 are inserted. The lower end of pins 18 have a portion of reduced diameter 21 which projects into corresponding radially spaced holes 22 on tube 19. The core 17 is therefore held against rotation by the guide tube. As indicated, both ends of the core are beveled inwardly toward the center and four equally spaced recesses 23 are drilled into each core end as shown in Fig. 5. The axis of these holes are parallel to the longitudinal axis of the core.

At the ends of the core 17 I provide cylindrical armature rings 24 and 25 having center openings. These are freely slidable longitudinally over the guide tube 19. A beveled face is provided on each armature at the end facing the core 17 that permits the armature to move snugly against the core face under the action of magnetic attraction. Radially spaced recesses 26- are provided in'the beveled armature faces so as to directly oppose the core recesses 23. Small springs 27 are inserted in these recesses as shown in Fig. 2 that normally urge the armatures outwardly and away from the core 17.

The forward armature 24 is limited in its outward movement by a forward end ring 26. This ring 26 is a circular metal disc with a center opening and contains a circular flange near its center which contacts a corresponding shoulder on the forward armature 24. The aft armature 25 passes through an aft end ring 28,-which is also a circular disc with a center opening, and is limited in its outward movement by. a stop 29. The spacing between'armatures and core is nicely set at about 0.001 inch. 7 i

The stop 29 is a circular member formed of insulating material which is inserted within the shell 13 against the end ring 28 and is pinned into place by pin 30. As shown in Fig. 2 stop 29-c0ntains a recess in which the two contact fingers 16 are supported. I bring the leads from the coil 14 through an opening 31 in end ring 23 and connect them to the contact fingers 16.

I locate within the guide tube 19 an elongated tubular plunger shaft 32 which is arranged to be reciprocally movable along its axis. The plunger 32 is countersunk at its aft end at 33 and is countersunk and threaded internally at its forward end at 34. At two spaced locations along the plunger 32 six radially spaced recesses are provided around the shaft periphery 35. This spacing is shown in Fig. 4. The guide tube 19 is provided with a shoulder 36 at its forward end and six radially spaced drilled holes 37 at two points around the tube periphery.

When the plunger shaft 32 is manually moved inwardly to the limit of its rearward travel in cocking or setting, the recesses are aligned with the holes 37. To hold the shaft 32 in thislocation chrome steel locking balls 28 are insertedin the space formed by the opposing recess and hole. In-this manner the balls ride in the tube hole 37 while projecting, a sufficient distance into the recess 35 to provide secure locking engagement with plunger shaft 32 and hold the shaft in cocked position. As seen in Fig.2, thebiasing of the shaft by its springs tendsto cam the balls outward due to-the contact of the edge ofrecesses 35' with the balls. The halls arelimited in their outward movement by the inner faces of armatures 24 and 25 which are spring biased into covering engagement by means of springs 27.

A circular groove 38 is cut into the forward face of tube shoulder 36. A plunger head 39 containing a short externally threaded shaft 40 is screwed into shaft recess 34 and is locked into place bymeans of pin 41. The inner face of head 39 contains a circular groove 42. A primary spring 43 and a smaller secondary spring 44 arranged in overlying relationship is positioned'between shoulder 36 and head 39 with the spring ends lying within grooves 38 and 42. 1

When the plunger shaft is moved rearwardly into the ball locking position the springs are compressed. When the locking means are released by outward movement of the balls the head 39 moves forward with great force and speed under the spring action to strike release lever 10 and release the bomb loads 11. I find that a spring force of about pounds issatisfactory.

The shell 13 is externally threaded for a short distance at its forward end. An end cap 45 is threaded onto the shell when the parts are assembled and when tightened a downwardly curving edge on the cap draws the tube shoulder 36 tightly against the end ring 26 to hold the plunger assembly rigidly in place. The end cap 45 at the forward end contains a U-shaped flange 46 which curves upwardly to form a circular seat 47. Another circular seat 43 is cut into the head 39 at its outer periphery.

In order to enclose the space between the head 39 and shoulder 36, in which the springs 43 and 44 are located, a flexible boot 49 of a rubber-like material is placed around the space and seated at either end within grooves 47 and 48. This boot 49 is of bellows-like shape and extends to allow the plunger shaft 32 to move forward to the full limit of its forward travel while continuing to enclose the space. The bellows is secured to seat 48 by means of two turns of stainless steel wire 50.

As discussed above, the head 39 is pushed inwardly manually and the plunger cocks by locking in the position of Fig. 2 through the previously described locking action of the balls 38. The extreme simplicity of this method of locking is very advantageous and merely a quick glance will reveal the position of the plunger.

-When it is desired to release the plunger 32 and actuate lever 10 the solenoid coil 14 is energized through the contacts 16. The resultant magnetic field magnetizes the core 17 and the armatures 24 and 25. are sharply drawn against the core, a meeting of the beveled faces thereby is effected. This movement takes place instantaneously with the energization of the coil and removes the restraining portion of. the armature from the upper surface of the balls 38. Instead recesses 51, which are machined into the lower outer edge of the armatures, are now brought into alignment with the six locking balls 38 at each end of the guide tube 19.

As discussedpreviously, the powerful action of springs 43 and 44 tends to urge the plunger 32 forwardly and the recesses 35 tend to cam the balls 38 outwardly but are prevented from so doing by the armature surfaces before the coil is energized. When, however, the solenoid coil is energized the armatures are moved and their recesses 51 aligned in the path of the balls, the balls are cammed outwardly from recesses 35, thereby releasing the plunger shaft. The plunger head consequently moves forward with great speed and force to strike the lever 10. The plunger in its released position is shown in Fig. 6 showing the locking balls in the position occupied after release. A quick and positive release action is thereby obtained.

To cushion the plunger 32 at the end of its forward travel a cup-shaped washer 52 is located directly behind the guide tube 19. The larger diameter outer edge of the washeris positioned within an internal shoulder of the stop*--29. An -O-ring 53' of resilient material is placedwithin the washer and when the plunger shaft 32 moves forward a flanged portion 54 on its end strikes the O-ring to limit the forward travel of the plunger shaft and cushion the impact.

An aft cap 55 is press-fitted into the countersunk opening 33 in the plunger shaft 32 aft end. This aft cap contains an internal opening into which is pressed a contact plunger 56. The contact 56 is utilized in a control relay and switching assembly for operation of an indicator light circuit and a transfer circuit not shown.

As seen in Fig. 6, I provide shallow recesses 57 on the periphery of the plunger shaft 32 to accommodate the locking balls when the plunger is in the released position.

The release mechanism of my invention is capable of exerting an extremely powerful force with its inherent characteristics and a positive strike on the bomb release shackle is insured. There is also an absolute minimum of delay between the time that the mechanism is energized and the time of the bomb release action which is of primary importance in aircraft bomb release equipment in order to assure accuracy. Assembly and disassembly of my invention is simplified by the small number of parts and there is consequently a substantial reduction in weight over the prior art devices. This is of paramount consideration in aircraft.

The release mechanism of my invention is outstanding by virtue of its characteristics of resisting any inadvertent or premature actuation due to shock loadsand at the same time being effective to operate when energized without failure. While sharp acceleration might tend to force one of the armatures against the core it will have an opposite effect on the other. And, correspondingly, while sudden deceleration would tend to force the other armature against the core it will not so effect the one. Nor will a roll, spin, quick turn or other maneuver introducing sharp centrifugal force cause a collapse of the armatures against the core and consequent premature actuation of the trip. My construction is such that any centrifugal forces are balanced out so that release is positively precluded.

Although my construction contemplates a pair of opposed armatures cooperating with a central core I find that certain benefits are had in a release or trip of general utility where but a single armature is employed and it is to be understood that such an embodiment is within the purview of my invention.

As many possible embodiments may be made of my invention, and as many changes may be made in the embodiment hereinbefore set forth, it is to be understood that all matter herein, whether described or illustrated is to be interpreted as illustrative and not as a limitation.

I claim as my invention:

1. A release mechanism comprising a loaded member; two individual locking means for retaining said member in cocked position; means surrounding said member and energizable .by electrical impulse for generating a magnetic field; a stationary core disposed within said magnetic field; and two opposed spring biased armatures disposed within said magnetic field and surrounding said member at opposite ends of said core and movable axially toward said core for releasing said locking means from said loaded member, one armature releasing one locking means and the other armature the other locking means, whereby said loaded member is moved into operative position upon application of said electrical impulse.

2. A release mechanism comprising a solenoid for generating a magnetic field; a hollow core positioned within said solenoid; a spring loaded plunger axially movable within said core; two spring biased armature rings positioned within said solenoid and surrounding said plunger, one at each end of said core; springs recessed in the faces of said armature rings and core for separating the same, said armature rings being movable toward said core by said magnetic field; and two locking means loaded by said plunger individually released by said rings thereby permitting the plunger to move into operative position,

3. An electrical release-mechanism comprising a spring loaded actuating plunger; a cylindrical guide member concentric with and surrounding said plunger; a core member concentric with and surrounding said cylindrical member and secured thereto; a solenoid coil concentric with and surrounding said core and energized by electrical energy to create a magnetic field; two opposed spring biased armatures, one positioned at each end of said core concentric with and surrounding said cylindrical member within said solenoid coil, said armatures being attracted to said core under the action of said magnetic field; and locking means individually cooperating with said armatures for retaining said plunger in the cocked position and released to unlocking position and actuation of said plunger under the action of said spring loading when said solenoid coil is energized and the armatures are attracted.

4. A release mechanism actuated by electrical energy, said mechanism comprising a cylindrical casing; a solenoid coil energizable by electrical energy for producing a magnetic field, said coil being concentric with and Within said casing, and containing a magnetizable core; a cylindrical member containing a plurality of ball locking means and positioned concentric with said core, with the ball locking means adjacent opposite ends of the core; a spring loaded plunger containing a plurality of spaced circumferential recesses engageable by said ball locking means to hold said plunger in the cocked position; and a plurality of spring biased armatures corresponding to said ball locking means and surrounding said ball locking means and attracted against said bias to said core by said magnetic field to permit release of said ball locking means, whereby said spring loaded plunger is sharply moved into release position upon energizing said solenoid coil.

5. A release mechanism actuated by electrical energy comprising a cylindrical casing; a solenoid coil positioned within said casing and energizable by the impulse for producing a magnetic field; a magnetizable core within said coil; tubular means retaining said core and coil within said casing and containing a plurality of spaced circumferential holes; two spring biased armature rings, one at a each end of said core and slidable on said tubular means; a spring loaded actuating plunger concentric with and within said tubular means and containing a plurality of a spaced recesses which are aligned with the holes in said tubular means when the plunger is in the cocked position; and locking balls retained by said spring biased rings engaging said recesses, said balls movable into unlocking position permitting release of said plunger into release position upon energizing said coil and attraction of said opposed armatures to said core.

6. An electrically actuated release mechanism comprising a spring loaded plunger member; a flexible en: closing boot secured to forward end of said member and enclosing said loading spring; two individual ball detent means for retaining said member in cocked position; solenoid means energized by electrical energy for generating a magnetic field, said solenoid means including a hollow core coaxially of said plunger member; and two spring biased means coaxially positioned with respect to said plunger member and at opposite ends of said core, said spring biased armature means movable axially against said bias upon energizing said solenoid and individually releasing said ball detent means, said loaded member being arranged to move into release position upon actuation of said ball detent means while expanding said enclosingflexible boot.

References Cited in the file of this patent France Dec. 8, 1937 

